Part 114 min

1.3 Struck-by and caught-in/between

Two of the Focus Four are about being in the wrong place when something moves. Struck-by is when an object hits you — a backing truck, a falling brick, a swinging load, a nail from a pneumatic gun. Caught-in or between is when you are crushed, pinched, or buried — a trench wall, a rotating shaft, a machine that started while you were inside it. They are grouped together in this chapter because the countermeasures overlap: control the energy, control the zone, and never be the thing that stops a moving mass.

1 Telling the two apart

The distinction sounds academic until you write an incident report. OSHA's rule of thumb: if the injury came from the impact of a moving object, it is struck-by. If the injury came from being squeezed, pinched, compressed, or crushed between two objects — or buried — it is caught-in/between. A worker hit by a falling load is struck-by; the same worker pinned between the load and a wall is caught-in/between.

Struck-by vehicle

Backing equipment, traffic, road work

Struck-by falling object

Loads, tools, materials from above

Caught between

Equipment and a fixed object, pinch points

Buried

Trench and excavation cave-ins

Both categories share a single geometric fact: they happen inside a zone. The swing radius of an excavator, the blind area behind a dump truck, the fall shadow under a crane load, the space between the trench wall and the bucket. Almost every control in this chapter is a way of keeping people out of a zone, or keeping the zone from moving.

2 Vehicles and mobile equipment

Construction sites run heavy equipment in tight spaces around workers on foot, often with the operator's view blocked. 29 CFR 1926.601 covers motor vehicles and 1926.602 covers earthmoving equipment, and both address the same problem.

Under 1926.601(b)(4), no employer may use motor vehicle equipment with an obstructed view to the rear unless the vehicle has a reverse signal alarm audible above the surrounding noise level, or the vehicle is backed only when an observer signals that it is safe. Under 1926.602(a)(9)(ii) the same rule applies to earthmoving and compacting equipment, and bidirectional machines such as rollers, compactors, front-end loaders and bulldozers must have a horn distinguishable from the surrounding noise, operated as needed when the machine moves in either direction.

1926.601(b)(14) adds the part crews skip: all vehicles in use shall be checked at the beginning of each shift — service brakes and trailer brake connections, parking brake, emergency stopping system, tires, horn, steering, coupling devices, seat belts, operating controls and safety devices — and all defects corrected before the vehicle is placed in service.

Common mistake: treating the backup alarm as the control. On a busy site everything beeps, and the alarm becomes background noise. The real control is a traffic plan: one-way routes, designated walking paths, a spotter with an agreed set of signals who stays out of the path, and eye contact with the operator before you cross behind anything.

3 Falling and flying objects

When employees are exposed to falling objects, 29 CFR 1926.501(c) requires the employer to have each employee wear a hard hat and to implement one of three measures: toeboards, screens or guardrail systems that keep objects from falling from the higher level; a canopy structure with materials kept back from the edge; or barricading the area below, prohibiting entry, and keeping objects far enough from the edge that they could not go over if displaced.

Read that carefully — the hard hat is in addition to, never instead of. A hard hat is rated for a modest impact from a modest mass; nothing worn on your head will save you from a dropped bundle of rebar. The controls that matter keep the object from coming down or keep you from being underneath.

Flying objects are the other half. Nail guns, grinders, chipping hammers, powder-actuated tools and compressed air all send fragments outward at speed, which is why eye and face protection (1926.102) sits in OSHA's top 10 and why chapter 2.2 of this course spends a full section on it.

On the job: the rule that prevents most dropped-object injuries is unwritten and simple — never work directly above or below another crew. When the schedule forces it, the lower crew moves, or a solid deck goes in between. "We'll be careful" is not one of the three options in 1926.501(c).

4 Cranes, loads and power lines

Suspended loads combine both hazards: struck-by if the load swings or drops, caught-in/between if it pins you, and electrocution if the boom finds a conductor. Subpart CC governs cranes and derricks in construction. The rule you should know by heart is in 29 CFR 1926.1408(a)(2): before operations begin, the employer must determine whether any part of the equipment, load line or load — including rigging and lifting accessories — could get closer than 20 feet to a power line when operated up to its maximum working radius. If it could, the employer must either confirm with the utility that the line is de-energized and visibly grounded, or maintain the 20-foot clearance with the specified precautions, or use the smaller minimum approach distances in the standard's Table A with those same precautions.

Those precautions (1926.1408(b)) include a planning meeting with the operator and everyone working around the load, non-conductive tag lines, an elevated warning line or barricade at the clearance distance in view of the operator, and at least one additional measure such as a proximity alarm, a dedicated spotter in continuous contact with the operator, a range limit device, or an insulating link.

Around any lift, the practical rules for a worker on the ground: stay out from under the load, stay out of the swing radius of the counterweight, handle loads with tag lines rather than hands, and never ride a load or a hook.

5 Trenches: the fastest caught-in hazard on any site

A cubic yard of soil weighs on the order of a small car, and a wall does not lean before it goes. Subpart P is short and unforgiving.

1
Protective system at 5 feet. 1926.652(a)(1): each employee in an excavation must be protected from cave-ins by an adequate protective system — sloping, benching, shoring, or a trench box — except in stable rock, or where the excavation is less than 5 feet deep and a competent person's examination gives no indication of a potential cave-in.
2
Sloping without soil classification. 1926.652(b)(1)(i): if the employer does not classify the soil, the excavation must be sloped no steeper than one and one-half horizontal to one vertical — 34 degrees from horizontal, the Type C configuration.
3
A way out at 4 feet. 1926.651(c)(2): trenches 4 feet or more deep need a stairway, ladder, ramp or other safe means of egress within 25 feet of lateral travel for every employee inside.
4
Spoil back from the edge. 1926.651(j)(2): excavated material and equipment must be kept at least 2 feet from the edge, or retained by a device that keeps it from falling or rolling in.
5
Locate utilities first. 1926.651(b)(1) and (b)(2): estimated locations must be determined before opening the excavation, and the utility owners contacted to establish the location of underground installations before digging starts.
6
Daily inspection. 1926.651(k)(1): a competent person inspects the excavation, adjacent areas and protective systems before the start of work, as needed through the shift, and after every rainstorm or other hazard-increasing occurrence. If they find a problem, exposed employees are removed until it is fixed.

Excavations deeper than 4 feet also carry an atmospheric requirement: under 1926.651(g)(1)(i), where oxygen deficiency — less than 19.5 percent oxygen — or another hazardous atmosphere exists or could reasonably be expected, the atmosphere must be tested before employees enter. Landfill areas and ground near stored hazardous substances are the examples the standard names.

6 Machines, guards and stored energy

The rest of caught-in/between happens at machines. 29 CFR 1926.300(b)(1) states the principle in one line: when power operated tools are designed to accommodate guards, they shall be equipped with such guards when in use. Paragraph (b)(2) requires that belts, gears, shafts, pulleys, sprockets, spindles, drums, flywheels, chains and other reciprocating, rotating or moving parts of equipment be guarded if an employee may come in contact with them.

Rotating equipment does not need much speed to be lethal. A shaft turning at a few hundred rpm will take a sleeve, a glove, a lanyard or long hair and everything attached to it faster than any reflex. That is the single reason loose clothing, dangling jewelry and — around rotating parts — gloves are the wrong choice, and why chapter 2.3 covers glove selection as a decision rather than a habit.

The other half is energy that is not obviously "on." Hydraulic pressure held in a cylinder, a raised bucket, a compressed spring, a capacitor, water in a line, and gravity itself will all move when a fitting is cracked or a pin is pulled. Servicing equipment means isolating and releasing that energy first, verifying zero energy, and preventing restart. In construction, 1926.417 requires that controls to be deactivated during work on energized or de-energized circuits be tagged, that de-energized equipment and circuits be rendered inoperative with tags attached at every point where they could be re-energized, and that the tags plainly identify what is being worked on. In general industry the full lockout/tagout program lives in 1910.147, and it is the fourth most cited standard in the country.

Common mistake: removing a guard "for one cut" and putting it back at the end of the day. The two most common caught-in injuries on a jobsite are a hand in an unguarded rotating part and a body between a machine and a fixed object during maintenance — both of them at the exact moment the work was "almost done."

Key takeaways

Struck-by is impact from a moving object; caught-in/between is being crushed, pinched or buried. Both happen inside a predictable zone.
1926.601(b)(4) and 1926.602(a)(9)(ii): no backing with an obstructed rear view unless there is a reverse alarm audible above the noise or a signaling observer; vehicles get a start-of-shift check under 1926.601(b)(14).
1926.501(c): hard hat plus toeboards/screens/guardrails, or a canopy, or a barricaded area below — the hat is never the only control.
1926.1408(a)(2): 20 feet of clearance from power lines up to 350 kV unless the line is de-energized and visibly grounded or Table A distances are used with the required precautions; tag lines must be non-conductive.
Trenches: protective system at 5 ft, egress within 25 ft of lateral travel at 4 ft, spoil back 2 ft, utilities located first, competent-person inspection daily and after rain.
1926.300(b): guards stay on when the tool is in use, and moving parts an employee can contact must be guarded; isolate and verify stored energy before servicing anything.

Free educational content — not OSHA-authorized training, no certificate or card issued. Follow your employer's program and the standards cited.